Projectile with fire-safe infra-red strike point marking

ABSTRACT

A projectile ( 100, 100   a,    100   b,    100   c ) containing two chemiluminescent dye components ( 123, 125 ), a dye powder ( 126 ) and one or more capsules ( 170 ) containing a pyrophoric substance. Upon impact at a target, a nose cap ( 110 ) of the projectile ( 100, 100   a,    100   b,    100   c ) and the capsule(s) ( 170 ) become broken, thereby allowing the pyrophoric substance to oxidize and emit an infra-red signal to mark the strike point. Oxidation of the pyrophoric substance is controlled, to allow the projectile to be fire-safe.

FIELD OF INVENTION

The present invention relates to projectiles with infra-red strike point marking. In particular, these projectiles are useful for training purposes or for use as marker rounds.

Background

Practice ammunition has been in use. For example, U.S. Pat. No. 7,004,074, assigned to Martin Electronics, describes a practice projectile 10 containing a powder dye charge 14 (see FIG. 1). After the projectile is fired, the nose cone 11 bonded to the projectile 12 ejects the dye at the point of impact. Due to the type of dye used, this projectile is limited to day-time use.

In another example, U.S. Pat. No. RE40,482, assigned to Nico-Pyrotechnik Hanns-Juergen, describes a practice projectile in which a marking agent is contained in a frangible hood at the head of the projectile. The marking agent consists of two chemical components contained in separate, adjacent compartments. These compartments share a common partition that has predetermined thin regions. When fired, the acceleration forces on the projectile break these thin wall regions to allow the two chemical components to react and give a chemo-luminescent light. The luminous light is emitted through the transparent hood while the projectile is in flight. Upon striking the target, the hood bursts to scatter the luminous chemical dye, thereby making the strike point optically visible. Due to use of the luminous dye, this projectile is limited to night-time use.

U.S. Pat. No. 7,475,638, also assigned to Nico-Pyrotechnik Hanns-Juergen, describes an improved projectile 50 that is usable for both day and night time use. In this projectile, two chemically active marking materials are separately contained in two containers 55, which are placed side-by-side to each (see FIG. 2). These containers 55 are then encased in an outer container 56. The outer container 56 is embedded in a dye powder 54 disposed inside a front cavity of the projectile. When the projectile 50 strikes a target, the front cavity bursts and the containers 55,56 become broken; as a result, the dye powder 54 is released and the two chemically active components react to give out light. There is still a need for the chemical reactions to give an optimal luminous effect.

It is appreciated that larger quantities of projectiles are used in training than in service; as such, cost becomes a very important factor in providing training projectiles. Coupled with limitations of known projectiles, it can thus be seen that there exists a need to provide projectiles with infra-red strike point marking to meet current and future challenges.

SUMMARY

The following presents a simplified summary to provide a basic understanding of the present invention. This summary is not an extensive overview of the invention, and is not intended to identify key features of the invention. Rather, it is to present some of the inventive concepts of this invention in a generalized form as a prelude to the detailed description that is to follow.

The present invention seeks to provide a frangible projectile with strike point marking for training purposes or for use as marker rounds during both day and night. The chemiluminescent dye material contained in the projectile is activated after the projectile is launched and the flight time allows the chemiluminescent dye to produce an effective glow at the point of impact. In addition, the pyrophoric substance is released at the point of impact to emit an infra-red signal.

In one embodiment, the present invention provides a projectile that emits an IR signal so that it is useful for night-time use. Another advantage is the projectile being fire-safe.

In one embodiment, the projectile comprises novel features as defined in the claims.

In another embodiment, the present invention provides a method of using the pyrophoric substance so that the projectile is fire-safe.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be described by way of non-limiting embodiments of the present invention, with reference to the accompanying drawings, in which:

FIG. 1 illustrates a known training ammunition as described in U.S. Pat. No. 7,004,074;

FIG. 2 illustrates another known training ammunition as described in U.S. Pat. No. 7,475,638;

FIG. 3A illustrates a cross-sectional view of a projectile according to an embodiment of the present invention;

FIG. 3B illustrates the placement of the pyrophoric capsules;

FIG. 3C illustrates a cross-sectional view of a projectile according to another embodiment of the present invention;

FIG. 3D illustrates a cross-sectional view of a projectile equipped with a two-part shield around the pyrophoric capsules; and

FIG. 4 illustrates a cross-sectional view of a projectile equipped with an integrally formed shield around the pyrophoric capsules.

DETAILED DESCRIPTION

One or more specific and alternative embodiments of the present invention will now be described with reference to the attached drawings. It shall be apparent to one skilled in the art, however, that this invention may be practiced without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals or series of numerals will be used throughout the figures when referring to the same or similar features common to the figures. Front/forward or rear orientation of any component is with respect to the travel direction of the projectile.

FIG. 3A shows a cross-section of a projectile 100 according to an embodiment of the present invention. As shown in FIG. 3A, the projectile 100 comprises a plastic hollow nose cap 110 threadably connected to a front end 141 of a projectile body 140, with a rear end of the projectile body 140 being connectable to a cartridge case 160. The plastic nose cap 110 is designed to break upon the projectile striking a target. The projectile 100 is generally elongate along a center axis C.

The front exterior of the nose cap or ogive 110 is substantially hemispherical in shape and it extends to its rear 116 in a cylindrical shape. As can be seen from FIG. 3A, the nose cap 110 forms a shell 112 and defines a cavity 118 therein. The shell 112 comprises two regions of varying thicknesses; the front hemispherical region 112 a is thick, and the rear cylindrical region 112 b is substantially thinner than the front region 112 a. The change in thickness between the two regions defines a line of weakness along which the nose cap 110 is susceptible to break upon experiencing an impact after the projectile 100 has been launched. The region of weakness on the wall of the ogive allows more effective outward sputtering or distribution of the payload and minimizes the pyrophoric component of the payload (discussed in greater detail below) from being trapped within the ogive cavity after impact, thereby reducing the chances of the broken projectile becoming a fire-hazard. In one embodiment, the nose cap 110 is made of a high-impact polycarbonate. Preferably, the nose cap 110 is translucent or opaque. In another embodiment, the ogive has a different shape to provide other technical effects. In addition, additional coatings or features can be applied or formed on the ogive to increase performance and safety reliability of the projectile.

A front end 141 of the projectile body 140 has a recess 146 at its center, with respect to the center axis C. The recess 146 is cylindrical in section and has a closed bottom. The exterior surface of the projectile body 140 located between the connections with the nose cap 110 and the cartridge case 160 has two projected rings 147. The ring surfaces have substantially the same exterior dimension as the cylindrical surface of the nose cap 110 so that they fit with a bore of a launcher (not shown in the figures) to spin stabilize the projectile 100 during launch and flight to the target.

As seen in FIG. 3A, an ampoule 122, disposed in the recess 146, occupies a space of the cavity 118 between the front interior end of the nose cap 110 and the projectile body 140. The ampoule 122 is a plastic container containing a first chemiluminescent dye component 123. Inside the ampoule 122 is a glass vial 124, which contains a second chemiluminescent dye component 125 that is reactive with the first chemiluminescent dye component 123 to give a luminous glow. The space in the cavity 118 surrounding the ampoule 122 is packed with a colored dye powder 126. Also as seen in FIG. 3A, a rubber 0-ring 130 is disposed in contiguous contact between the ampoule 122 and the inside surface of the front hemispherical region 112 a of the shell 112.

Still referring to FIG. 3A, capsules 170 containing a pyrophoric substance is disposed at the front end 141 of the projectile body 140 and are packed in position by the dye powder 126. Preferably, there are two or more of the capsules 170 in each projectile. Preferably, the amount of pyrophoric substance contained in each of the capsules is substantially about 500 mg; this amount of pyrophoric substance has been tested to burn for a short duration to emit an infra-red signal that is noticeably detectable and yet does not create a fire hazard; this projectile 100 is advantageous for use in training grounds that are dry and susceptible to catch fire; in other words, the use of this projectile allows a user to mark the strike point with a fire-safe thermal signature. In one embodiment, the pyrophoric substance is iron-based. In another embodiment, the pyrophoric substance is based on other element or a combination of several elements. Preferably, the pyrophoric substance has a super fast burning rate, that is, a variant that burns with high heat but for a short duration of time. A balance between high heat and short duration of burning is achieved so that an optimal amount of infra-red signal is emitted yet keeping the projectile fire-safe.

FIG. 3B illustrates a plan view when looking at the front end 141 of the projectile body 140. For illustration purposes, FIG. 3B shows there are 4 capsules 170 being spatially disposed in an annular area around the center axis of the projectile 100. In one embodiment, the capsules are directly embedded in the compacted dye powder 126. In another embodiment, the capsules 170 are supported on an annular ring 175 that is embedded in the dye powder 126. In other words, the capsules 170 are spatially placed on the support ring 175 and the dye powder 126 is used to fill the spaces between the capsules 170 and to keep the capsules in position. The support ring 175 is to ensure that the capsules 170 remain in position in the projectile 100 because the dye powder 126 and the capsules 170 have different specific densities; preferably, the support ring 175 is made of paper, such as wax paper; cotton or textile fibers, woven or non-woven; plastic material; foams; and so on; advantageously, the support ring is biodegradable. The number of capsules 170 shown in FIG. 3B is for illustration and is not so limited; the number of capsules can be few or more.

FIG. 3C shows a cross-section of a projectile 100 a according to another embodiment of the present invention. The projectile 100 a is similar to the above projectile 100 except that the front end 141 of the projectile body is made up of two components, 140 a and 140 b. By providing the front portion 140 a of the projectile body 140 as a separate piece, it serves as a filler plug for the dye powder 126 and it makes filling of the dye powder 126 into the cavity 118 and subsequent assembly of the projectile 100 a easier. In another embodiment of the projectile, the dye powder 126 is pre-packed in sachets 126 a (not shown in the figures), where each sachet 126 a is packed into the cavity 118 surrounding the ampoule 122.

FIG. 3D shows a cross-section of a projectile 100 b according to another embodiment of the present invention. Projectile 100 b is shown with substantially the same construction of the projectile 100,100 a but with a shield 180 disposed between the ampoule 122 and the front end 141 of the projectile body 140. The shield 180 is used to minimize the chemiluminescent dye components 123, 125 from adversely wetting the pyrophoric substance when these liquid chemical components are being sputtered out after the projectile 100 b strikes a target or ground. As can been seen in FIG. 3D, the shield 180 is cylindrical in shape; the shield 180 may have a length of substantially one third to half the depth of the recess 146. In one embodiment, the shield 180 is made of paper, for example, wax paper, which is biodegradable. In another embodiment, the shield 180 is made of paper deposited with a layer of aluminium or made of an aluminium foil. The shield 180 can be wrapped around the ampoule 122 or attached on the ampoule 122 in the form of an adhesive tape. In another embodiment (not shown in the figures), the shield 180 and the support ring 175 are mortised together; in another embodiment, the shield 180 and the support ring 175 are glued together. Another shield can also be added between the dye powder 126 and the pyrophoric capsules 170 to ensure that the pyrophoric substance will not be smothered by the dye powder 126; alternatively, the shield between the dye powder 126 and the pyrophoric capsules 170 is an extension of the shield between the ampoule 122 and the front end 141 of the projectile body.

In another embodiment 100 c, the shield 180 and support ring are integrally formed from one piece, for example, with corrugations like those paper cups for muffins; FIG. 4 shows a side view of such an integrally formed shield 180 a. In yet another embodiment (not shown), a shield 180 b is formed from a cylindrical shape with one end being cut and the ends are folded out to provide support for the capsules 170; in use, the folded ends of the shield 180 b are being embedded in the dye powder 126 like in the above embodiments.

In use, after the projectile 100, 100 a, 100 b, 100 c is ejected from a launcher, the projectile 100, 100 a, 100 b, 100 c experiences large acceleration and spin forces; as a result, the impulse imparted onto the glass vial 124 in the ampoule 122 causes the vial to break and the first and second chemiluminescent dye components 123,125 to mix within the ampoule 122 and react with each other. The spin forces also cause turbulent mixing of the first and second chemiluminescent dye components 123,125 to give a luminous glow, even when the projectile 100, 100 a, etc is in flight. When the projectile 100, 100 a, 100 b, 100 c hits its target, the impact of the projectile 100, 100 a, 100 b, 100 c causes both the plastic nose cap 110, the ampoule 122 and the capsules 170 to break. As a result, the dye powder 126, the glowing chemiluminescent dye material and pyrophoric substance are dispersed at the point of impact. When the pyrophoric substance is released from the capsules 170, the material begins to oxidize and emits an infra-red signal that is detectable with suitable IR detection devices, such as night vision goggles or thermal imaging cameras. The impact forces also cause the dye powder 126 to sputter and to provide a visible effect at the point of impact during day-time training. The sputtering of the dye powder 126 carries with it the chemiluminous dye, causing the point of impact to be more visible from a distance.

In the above embodiments, ballistic performance of the projectiles 100,100 a,100 b, 100 c is desirably as close as possible to the ballistic performance of projectiles in service. To achieve this, tests with projectiles made of different materials and mass distributions of the components were carried out. In addition, safety tests, such as drop test, were carried out to ensure that these projectiles 100,100 a, 100 b, 100 c are strong enough to withstand handling during transportation and foreseeable types of mishandling.

While specific embodiments have been described and illustrated, it is understood that many changes, modifications, variations and combinations thereof could be made to the present invention without departing from the scope of the present invention. For example, a large caliber projectile may be similarly configured like the above projectiles for both day and night strike point marking. In another example, a grenade may also be similarly configured according to the teaching of the present invention. In another example, the materials of the ampoule and vial are not limited, respectively, to plastic and glass; they Can be made of other materials to store the chemiluminescent dye components. 

1. A projectile having an elongate body, which defines a longitudinal axis, with a front portion being connectable to a hollow nose cap and a rear portion connectable to a cartridge case, the projectile comprising: an ampoule disposed inside the hollow nose cap, with the ampoule's longitudinal axis substantially coaxial with the longitudinal axis of the projectile, and the ampoule containing a first luminescent dye component; a vial disposed inside the ampoule, with the vial containing a second luminescent dye component; a dye powder filing a cavity between the hollow nose cap, the ampoule and the front portion of the projectile body; and one or more capsules containing a pyrophoric substance, with the one or more capsules being disposed in the dye powder and at the front portion of the projectile body; wherein, upon the projectile striking a target, the nose cap and the one or more capsules become broken, thereby allowing the pyrophoric substance to oxidize and to emit an infrared signal to mark the point of impact.
 2. The projectile according to claim 1, further comprising a support ring to maintain the one or more capsules at the front end of the projectile body.
 3. The projectile according to claim 2, further comprising a shield disposed between the one or more capsules and the ampoule.
 4. The projectile according to claim 2, wherein the support ring and the shield are made of paper.
 5. The projectile according to claim 4, wherein the support ring and shield are mortised or glued together.
 6. The projectile according to claim 4, wherein the support ring and shield are integrally formed in one piece by corrugations.
 7. The projectile according to claim 4, wherein the shield is cylindrical and the support ring is constituted by flaps folded out from one end of the cylindrical shield.
 8. A method of marking a strike point of a projectile with an infra-red signature, the method comprising: breaking a nose cap on a projectile and one or more capsules containing a pyrophoric substance by impact forces after the projectile strikes a target or ground, and allowing the pyrophoric substance to oxidize for a short duration of time so that the infra-red signature is detectable by a thermal camera, yet keeping the broken projectile fire-safe.
 9. A use of an infra-red emitter using a pyrophoric substance having a short burn duration in a fire-safe projectile. 